How to return data when back to previous activity

main.dart

import 'package:flutter/material.dart';

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
      debugShowCheckedModeBanner: false,
      home: MyWidget(),
    );
  }
}

class MyWidget extends StatelessWidget {  
  @override
  Widget build(BuildContext context) {
    return Scaffold (
      body: Column(
        children: [
          ElevatedButton(
            onPressed: () async {
              String textFromPageB = await Navigator.push(
                context,
                MaterialPageRoute(
                  builder: (_) => PageB(),
              ));
              print(textFromPageB);
            },
            child: Text('Go to Page B'),
          ),
        ]
      )
    );
  }
}

class PageB extends StatelessWidget {
  @override
  Widget build(BuildContext context){
    return ElevatedButton(
            onPressed: () async {
              Navigator.pop(context, "My Message");
            },
            child: Text('Go back'),
          );
  }
}